Conventionally, various systems have been provided as a means for controlling the direction of the optical axes of vehicle headlights. An example of the systems is disclosed in Patent Document 1. The system described in Patent Document 1 (title of the invention is “Apparatus for recognizing traveling vehicles”) picks up images in color in the forward direction of the vehicle to obtain images in color. Image signals corresponding to tail lights and headlights are extracted from the signals of the color image to recognize the presence of tail lights or headlights. Of these signals, the image of tail lights is used to calculate a distance to the forward vehicle and a relative speed. Based on the calculation result, the headlights are controlled, for example, so as to be switched to low beam.
In order to perform a series of processes of the control, the type of a light source is required to be determined. In this regard, Patent Document 1 provides a method of determining the type of a light source, which is based on a color (balance of RGB signals) detected in an area of a light source in a picked-up image.